In a mobile communications system, during transmission in a radio channel, a signal is affected by various factors that may cause signal fading, for example, a path loss. A main technical means for overcoming channel fading is power control: on the basis of evaluating of indexes of a receive end such as a received signal strength and/or a signal-to-noise ratio, transmit power of a transmit end is changed in time to compensate for the path loss and fading in the radio channel, thereby maintaining communication quality. Power control technologies comprise an open-loop power control technical solution, a closed-loop power control technical solution and an open-loop and closed-loop joint power control technical solution. In the open-loop power control technical solution, a transmit end measures a downlink reference signal from a target receive end in an idle timeslot, estimates a downlink path loss value with reference to transmit power of the downlink reference signal, and performs, when sending an uplink signal to the receive end, uplink path loss compensation according to a correlation between an uplink path and a downlink path and based on, for example, a downlink path loss value obtained at the last time, so as to determine transmit power. In the closed-loop power control technical solution, a receive end measures an uplink signal sent by a transmit end at the previous time, calculates a power adjustment value to obtain a power control command, and sends the power control command to the transmit end, and the transmit end adjusts current transmit power according to the power control command, thereby compensating for a channel quality change generated in the transmit end because of quick fading. In the open-loop and closed-loop joint power control technical solution, a transmit end sets transmit power with reference to transmit power obtained by means of open-loop power control and a power control command obtained by means of closed-loop power control.
In the foregoing open-loop power control solution, a path loss is generally calculated during an idle timeslot. During continuous signal transmission, transmit power is always determined according to a path loss calculated at the last time. For example, during an entire uplink timeslot or frame or subframe, uplink transmit power is the same. However, an actual path loss, affected by various factors such as an environment change, and an atmosphere condition, actually continuously changes with time. Consequently, signal power actually received by a receive end does not conform to expected receive power, or in other words, does not conform to an expected signal-to-noise ratio. Moreover, in the foregoing closed-loop power control solution, although the power control command is determined before the uplink signal is sent, the path loss that continuously changes with the time, an interference and the like cannot be rapidly used.